1. Field of the Invention
The present invention relates to a method of embedding interleaved servo information fields onto a disk used as a storage medium for a disk drive, and a disk having interleaved servo information fields embedded thereon for use as a storage medium for a disk drive.
2. Description of the Related Art
Disks used as storage mediums for conventional disk drive assemblies typically have embedded sector servo position information inserted thereon for closed loop GMR (giant magnetoresistive) head or MR (magnetoresistive) head position control. The embedded sector servo position information fields include information that generally provides timing reference, track identification, and fine track burst information. The head position system controls the position of the head carrier within the disk drive assembly, so that the read and write heads stay on the desired data track of the disk to read and write data accurately. The sector servo position information fields are exclusively used by the head position system, and cannot be used for storage of general data. The area of the disk surface allotted for embedded sector servo position information is thus overhead with respect to disk storage area. As disk capacity and TPI (track per inch) of current disk technology increase, the total number of sector servo position information fields on the track necessary to meet performance and shock vibration requirements also increases.
FIG. 1 illustrates a typical disk drive assembly 100 including spindle 104, disk platter surface 102, actuator arm 114, head carrier 110, servo positioning motor 116, counter balance arm 118, servo controller 120 and servo control circuit board 122. The disk platter surface 102 may be coated with a ferro-magnetic material suitable for storing magnetic information. The mechanical layout of actuator arm 114 including a read and write head, as related to disk platter 102 and the disk drive chassis, is described in U.S. Pat. No. 6,049,440, which is hereby incorporated by reference in its entirety for all purposes.
FIG. 2A illustrates conventional embedded sector servo position fields 200 inserted between data fields 250 of a track on a disk of a conventional disk drive assembly. The conventional sector servo position information fields 200 generally include a servo preamble, a servo address mark, a servo gray code and index, and servo bursts A, B, C and D, as illustrated in greater detail in FIG. 2B. However, as disk capacity and TPI for disks of the conventional head drive assemblies have increased, compensation for spindle repetitive run-out (RRO) has become necessary.
As additional background, a servo preamble is a field typically used by a servo circuit in the data channel ASIC chip for servo circuit AGC (automatic gain control) and servo bit signal phase synchronization. During this field, the servo circuits establish proper signal amplitude and correct phase alignment for the servo address mark and following servo gray code and index field decoding. The servo address mark is a unique pattern field occurring after the servo preamble. The pattern is typically selected as a pattern having the least possibility of detection as actual data over the entirety of the track including the data field. Once the pattern is detected, a correct location on the track such as a mark on the disk can be used as a reference. This pattern field establishes the basic timing reference for the servo gray code and index field, as well as the reference timing for the burst field. The servo gray code and index field contains the servo track address, and may also include the servo sector address number and head number. Gray code encoding is typically used so that only one address bit changes from one track address to the next track address. The index typically is the first servo sector address number to indicate the beginning of a track. A servo sector address number (corresponding to the sequences of the servo sector field) may reach a few hundred. The servo burst field includes several burst fields for generating a position signal. A 4-burst scheme is widely used. A 6-burst scheme may be used to provide better linearity for the position signal, with an additional 2-burst overhead however.
FIG. 3A illustrates a conventional track layout for a disk of a hard drive assembly, the track layout including embedded sector servo fields 300 inserted between data fields 350. In this conventional track layout, a respective RRO field 303 is included for each sector servo field 300. RRO field 303 is servo correction information that is used to compensate RRO during track following. In the track layout as illustrated in FIG. 3A, each RRO field 303 is used to compensate RRO during both reading and writing of the data fields, under the condition that offset between the MR head write element and read element on the head carrier is minimal. Additionally, a track servo parameter preamble and a track servo parameter sync mark, indicated as field 302, is appended to each RRO field 303, to enable the RRO field to be read.
In general, RRO fields 303 typically contain an RRO value and a few information control bits such as a defect bit, or other information bits to indicate the condition of the data field or the servo field itself (like bad, poor or good, for example). The RRO value is the compensation value for track following. Fields 302 and 303 are written onto the disk during manufacturing of the disk drive assembly. After several rounds of reading a position signal derived from a 4-burst or a 6-burst field, the analysis of these position signals provides information about spindle motor run-out. The badly written burst fields and/or defects can also be identified. The RRO value is the cancellation value that compensates the spindle motor repetitive run-out to allow the head to stay on the track, to prevent the MR head from wandering away from the desired track.
FIG. 3B illustrates a conventional track layout including embedded sector servo fields 300 inserted between data fields 350, that is similar to the conventional track layout of FIG. 3A. However, separate write and read RRO fields 308 and 309 are respectively provided for each sector servo position field 300. Each of the write RRO fields 308 include a corresponding write track servo parameter preamble and write track servo sync mark field 302, and each of the read RRO fields 309 include a corresponding read track servo parameter preamble and read track servo sync mark field 302. By using separate write RRO fields and read RRO fields, better track registration and performance may be achieved in a case wherein large offset is present between the MR head write element and read element on the head carrier.
The above described embedded sector servo fields including the servo correction information are inserted on the disk surface in pie-shaped sectors by the disk drive assembly manufacturer, as illustrated in FIG. 4. The various tracks 1000, 1001 and 1002 are divided into sectors 1003, 1004 and 1005 for example, wherein embedded sector servo information fields 1006 including the servo correction information as described above are inserted on every track at a corresponding sector boundary. Conventionally, the sector servo information fields are each the same size and are equally spaced on the disk surface. The embedded sector servo area overhead of the disk surface is the ratio of the area used for head position servo fields to the area used for data storage. As may be particularly understood in view of FIG. 4, embedded sector servo area overhead of a typical disk is high. Thus, the disk surface area that may be used for data storage is limited, and this becomes especially noticeable as disk capacity and TPI rate of current disk technology increase.
The present invention is therefore directed to a method of interleaving servo information fields onto a track of a recording medium, and a recording medium having at least one track with data fields and servo fields interleaved thereon, which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art.
An object of the invention is to thus reduce embedded sector servo area overhead on the disk surface, so that data storage area on the disk may be increased.
The above and other objects may be achieved by a method of interleaving servo information fields onto a track of a recording medium, including inserting data fields onto the track; inserting a first servo field onto the track, the first servo field including servo correction information that is used for accessing the data fields; and inserting a second servo field onto the track, the second servo field being a reduced servo field that is used for accessing the data fields and that does not include servo correction information. The servo correction information of the first servo field includes first servo correction information for the first servo field and second servo correction information for the second servo field. The servo correction information may be repetitive run-out (RRO) cancellation values that are used for accessing the data fields and information status bits used to indicate the condition of the servo and data fields.
The above and other objects may also be achieved by a recording medium having at least one track with data fields and servo fields interleaved thereon, the recording medium including a first servo field inserted onto the at least one track, the first servo field including servo correction information that is used for accessing the data fields; and a second servo field inserted onto the at least one track, the second servo field being a reduced servo field that is used for accessing the data fields and that does not including servo correction information. The servo correction information of the first servo field includes first servo correction information for the first servo field and second servo correction information for the second servo field. The servo correction information may include repetitive run-out (RRO) cancellation values that are used for accessing the data fields and information status bits used to indicate the condition of the servo and data fields.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.